When printing machine cylinders formed with grooves roll off against each other, shocks result as the circumference of the cylinders changes from a smooth circumferential region to the groove, and back to another smooth circumferential region. Usually, these cylinders are blanket cylinders, such as rubber blanket cylinders in rotary offset printing machines.
The referenced U.S. Pat. No. 4,742,769, assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference, describes a rail-like filler element which, preferably, in cross section is essentially mushroom-shaped. It can be engaged against the bottom of a blanket attachment groove, either directly or indirectly. Such fillers provide for damping of impacts which arise as cylinders roll off against the grooves. Reducing these impacts improves the quality of printing. The filler insert described in the aforementioned patent is of relatively short axial length. When two cylinders roll off against each other, while being pressed against each other with substantial force, which may be in the order of one or two tons, the filler elements are highly loaded because, due to the comparatively short axial extent, the per square unit load placed thereon is very high. As a consequence, the filler element is subject to wear and tear and, further, expensive specialty high wear resistant materials must be used.
Other filler elements have been proposed, for example as described in German Patent 36 44 501, which are of about the same length as the cylinder; these filler elements, it has been found, have insufficient effect with respect to damping of shocks arising as printing machine cylinders roll off against each other at the grooves. It appears that this is due to the extreme loading at the edge regions, that is, at the ends of the cylinders applied against the filler elements; at central portions of the cylinder, the loading is low and no supporting effect will be obtained.